The recent description of biallelic DNAJC30 variants in Leber hereditary optic neuropathy (LHON) and Leigh syndrome (LS) challenged the longstanding assumption for LHON to be exclusively maternally inherited and broadened the genetic spectrum of LS, the most frequent paediatric mitochondrial disease. Herein, we characterise 28 so far unreported individuals from 26 families carrying a homozygous DNAJC30 p.Tyr51Cys founder variant, 24 manifesting with LHON, two manifesting with LS, and two remaining asymptomatic. This collection of unreported variant carriers confirms sex-dependent incomplete penetrance of the homozygous variant given a significant male predominance of disease and the report of asymptomatic homozygous variant carriers. The autosomal recessive LHON (arLHON) patients demonstrate an earlier age of disease onset and a higher rate of idebenone-treated and spontaneous recovery of vision in comparison to reported figures for maternally inherited disease (mtLHON). Moreover, the report of two additional patients with childhood- or adult-onset LS further evidences the association of DNAJC30 with LS, previously only reported in a single childhood-onset case.

BRG1/BRM-associated factor (BAF) complex is a chromatin remodeling complex that plays a critical role in gene regulation. Defects in the genes encoding BAF subunits lead to BAFopathies, a group of neurodevelopmental disorders with extensive locus and phenotypic heterogeneity. Methods: We retrospectively analyzed data from 16,243 patients referred for clinical exome sequencing (ES) with a focus on the BAF complex. We applied a genotype-first approach, combining predicted genic constraints to propose candidate BAFopathy genes. Results: We identified 127 patients carrying pathogenic variants, likely pathogenic variants, or de novo variants of unknown clinical significance in 11 known BAFopathy genes. Those include 34 patients molecularly diagnosed using ES reanalysis with new gene-disease evidence (n = 21) or variant reclassifications in known BAFopathy genes (n = 13). We also identified de novo or predicted loss-of-function variants in 4 candidate BAFopathy genes, including ACTL6A, BICRA (implicated in Coffin-Siris syndrome during this study), PBRM1, and SMARCC1. Conclusion: We report the mutational spectrum of BAFopathies in an ES cohort. A genotypedriven and pathway-based reanalysis of ES data identified new evidence for candidate genes involved in BAFopathies. Further mechanistic and phenotypic characterization of additional patients are warranted to confirm their roles in human disease and to delineate their associated phenotypic spectrums.

SUMMARY A biochemical screening scheme on agar media for differentiating Enterobacteriaceae in a hospital laboratory is evaluated. Careful observation of test reactions within the scheme permitted the recognition of 78 biotypic reaction patterns which could contribute to epidemiological surveillance. The limitations of the technique are described and discussed and methods of importance in ensuring the reproducibility of reaction patterns emphasised.